No standardized susceptibility testing procedures exist for rapidly- growing mycobacteria or Nocardia species. Several different procedures have been suggested for use, including broth microdilution and the Etest (manufactured by AB Biodisk, Culver City, CA). The Etest produces results which are difficult to interpret with these organisms, and we do not plan to do any further work with this procedure for these organisms at present. We were collaborators in a multi-institution study to determine the inter- and intra-institution reproducibility of both the Etest and a microdilution procedure for susceptibility testing of rapidly-growing mycobacteria. The results of the microdilution procedure from this study have been analyzed, and the results have been published (Woods GL, et al, J. Clin. Microbiol. 1999;37:1676-1682). The microdilution procedure employed will probably become the reference procedure for susceptibility testing of rapidly-growing mycobacteria. This project is terminated.